1. Field of the Invention
The present invention relates to a photoelectric converting device having a guide member, and, more particularly, to a photoelectric converting device having a guide member which can be suitably used in an input portion of an image processing apparatus such as a facsimile machine, an image reader, a digital copying machine, an electronic blackboard and the like for reading image information of an original sheet by relatively moving the original sheet the image of which is to be read while bringing the original sheet into closely contact with a one-dimensional line sensor.
2. Description of the Prior Art
Recently, an elongated line sensor, which can be used in an equal magnification optical system, has been developed as a photoelectric converting device for the purpose of reducing the size and improving the performance of an image processing apparatus such as a facsimile machine and an image reader and the like.
In order to reduce the size and the cost of an image processing apparatus of the type described above, a photoelectric converting device having a guide member have been disclosed which is constituted in such a manner that the equal magnification fiber lens array is replaced by a structure in which light reflected from the original sheet is directly detected by a sensor via a transparent spacer made of, for example, glass.
FIG. 1 is a schematic cross sectional view which illustrates a conventional photoelectric converting device when viewed from the main scanning direction of a photoelectric converting element array thereof.
Referring to FIG. 1, reference numeral 1 represents a light transmissive sensor substrate constituted in such a manner that a photoelectric converting element (omitted from illustration) is formed on a light transmissive substrate made of glass or the like by a semiconductor manufacturing process or the like. A transparent protection layer 2 made of a thin glass plate or the like is formed on the photoelectric converting element.
The light transmissive sensor substrate 1 is secured to a base plate 3 made of aluminum or the like.
An illumination opening 5 through which illumination light L emitted from a light source 4 passes is formed in a portion of the base plate 3. Reference numeral 4 represents the above-described light source for illuminating original sheet P, the light source 4 comprising an LED array composed by arranging a plurality of LED chips in an array-like configuration.
Reference numeral 6 represents a conveyance roller for conveying the original sheet P by bringing the original sheet P into contact with the transparent protection layer 2.
As a result of the structure thus constituted, illumination light L emitted from the light source 4 passes through the light transmissive sensor substrate 1 before it illuminates the original sheet P. Light corresponding to information about the original sheet P and reflected from the same is made incident upon the photoelectric converting device disposed on the light transmissive sensor substrate 1 so that it is converted into an electric signal before transmitted as an image signal.
Referring to FIG. 1, original-sheet conveyance guide means 7 is disposed on the light transmissive sensor substrate 1 on the original-sheet supply side which opposes the original-sheet conveying direction. The structure shown in FIG. 1 is arranged in such a manner that a portion of the base plate 3 is arranged to project so that the original sheet P passes over the surface of the thus formed projection.
Usually, the light transmissive sensor substrate 1 is arranged in such a manner that a multiplicity of photoelectric converting element arrays are, by the semiconductor manufacturing process, formed on the large size glass substrate and the glass substrate is then sectioned into pieces each of which contains the photoelectric converting element array by using a slicer or the like. Therefore, there arises a problem in that burrs (omitted from illustration) such as chipping are formed at the edge of the light transmissive sensor substrate 1.
Accordingly, a structure has been employed in which a gap the size of which corresponds to the size of the burrs which will be formed at the edge of the light transmissive sensor substrate 1 is provided between the guide means 7 and the light transmissive sensor substrate 1.
However, the front portion of the original sheet P will be caught by the above-described gap, causing a jam to occur after the front portion of the original sheet P has been conveyed toward the read portion from the original-sheet supply side.
Therefore, the conventional photoelectric converting device has been arranged in such a manner that the height of the guide means 7 is made larger than that of the light transmissive sensor substrate 1 so that the above-described problem takes place in that the front portion of the original sheet can be caught by the gap.
However, the above-described conventional photoelectric converting device of the type described above has the following problems in the case where the overall cost and the size of the photoelectric converting device are desired to be reduced.
In order to reduce the overall cost and the size of the photoelectric converting device, it might be considered feasible to employ a method arranged in such a manner that the width of the light transmissive sensor substrate, that is, the width of the light transmissive sensor substrate in the direction in which the original sheet is conveyed, is reduced so that the number of the sections of the large-size substrate including the photoelectric converting devices is enlarged.
However, in the case where the width of the light transmissive sensor substrate 1 in the direction in which the original sheet is conveyed is reduced, the front portion of the guide means 7 and the conveyance roller 6 undesirably come closer to each other, causing the space in which the original sheet is conveyed to be reduced. As a result, a jam will easily occur in accordance with the state of the front portion of the original sheet.
For example in a case where an original sheet having a small thickness is conveyed, the front portion of the original sheet usually has a curvature (the front portion of the original sheet usually curves). Therefore, a jam will occur.
Furthermore, in a case where an original sheet having a large thickness is conveyed, the rigidity of the original sheet is too strong, causing the original sheet to positioned farther from the protection layer. As a result, the depth of field cannot be maintained, causing the S/N ratio to deteriorate critically.
Another disclosure has been made which is, as shown in FIG. 2, arranged in such a manner that the protection layer 2 of the light transmissive sensor substrate 1 and the guide means 7 for conveying the original sheet are combined into one component so as to overcome the above-described problem experienced with the above-described conventional photoelectric converting device.
However, it is very difficult to select a material which is able to perform both the function as the protection layer and the function as the guide means. Therefore, there have been unsolved problems in terms of the overall performance of the photoelectric converting device and the reduction in the maintenance cost.
For example, in a case where an organic film is employed as the above-described material serving as the above-described two functions, damages occur in the surface of the film and dust adheres to the same due to the large frictional force generated while conveying the original sheet. As a result, a problem arises in that the S/N ratio will deteriorate with the lapse of time.